Thermoplastic polymer compositions and process of making the same

ABSTRACT

THERMOPLASTIC VINYL RESINS HAVING HIGH TRANSPARENCY AND HIGH IMPACT RESISTANCE, CONSISTING OF A POLYBUTADIENCE INTERPOLYMER OR CONTAINING SUCH INTERPOLYMER BLENDED WITH A VINYL CHLORIDE POLYMER, SAID INTERPOLYMER BEING FORMED IN TWO STAGES, IN THE FIRST OF WHICH A BUTADIENCE POLYMER CONSISTING OF POLYBUTADIENNE OR CONTAINING AT LEAST 50% BUTADIENCE IS POLYMERIZED WITH MONOMERIC METHYL METHACRYLATE AND IN THE SECOND OF WHICH, MONOMERIC AROMATIC VINYL COMPOUND IS POLYMERIZED WITH THE GRAFT POLYMER FORMED IN THE FIRST STAGE, THE METHYL METHACRYLATE COMPRISING FROM 10% TO 80% OF THE TOTAL MONOMER ADDITION, AND THE VINYL AROMATIC MONOMER COMPRISING FROM 90% TO 20% THEREOF; SUCH POLYMERIZATION BEING EFFECTED IN AN AQUEOUS MEDIUM WHICH CONTAINS, IN RELATION TO 100 PARTS OF TOTAL RESINOUS CONSTITUENTS, FROM 0.5 TO 10.0 PARTS OF FORMALDEHYDE SULFOXYLIC SALT AND EFFECTIVE AMOUNTS UP TO 3 PARTS OF PEROXIDES; AT LEAST 80% OF SAID BUTADIENCE POLYMER AT THE START BEING IN THE FORM OF PARTICLES BELOW 0.2U IN DIAMETER WHERE ITHE INTERPOLYMER IS TO BE BLENDED WITH VINYL CHLORIDE, AND BELOW 0.1U IN DIAMETER WHERE THE INTERPOLYMER IS TO BE USED ALONE; SAID BUTADIENCE POLYMERIC MATERIAL CONSTITUTING OUT OF EACH 100 PARTS OF TOTAL RESINOUS CONSTITUENTS, FROM 20 TO 70 PARTS WHEN THE INERPOLYMER IS TO BE BLENDED WITH VINYL CHLORIDE POLYMER, AND FROM 20 TO60 PARTS WHEN THE INTERPOLYMER IS TO BE USED ALONE, THE REMAINDER OF EACH 100 PARTS CONSISTING OF THE SUM OF THE MONOMERIC ADDITIONS.

United States Patent Oflice 3,651,177 Patented Mar. 21, 1972 3,651,177THERMOPLASTIC POLYMER COMPOSITIONS AND PROCESS OF MAKING THE SAME KazuoSaito, 912 Irving Ave., Syracuse, N.Y. 13210; and Takeshi Tanaka andIchiro Saito, both of 700 Torigai-mishi, Mishima-cho, Osaka, Japan NoDrawing. Continuation of applications Ser. No. 470,193, July 7, 1965,and Ser. No. 502,396, Oct. 22, 1965. This application June 27, 1969,Ser. No. 837,310

Claims priority, application Japan, Jan. 25, 1965,

40/ 3,924, 40/ 3,926 Int. Cl. C08f 19/08, 41/12 U.S. Cl. 260-876 R 15Claims ABSTRACT OF THE DISCLOSURE Thermoplastic vinyl resins having hightransparency and high impact resistance, consisting of a polybutadieneinterpolymer or containing such interpolymer blended with a vinylchloride polymer, said interpolymer being formed in two stages, in thefirst of which a butadiene polymer consisting of polybutadiene orcontaining at least 50% butadiene is polymerized with monomeric methylmethacrylate and in the second of which, monomeric aromatic vinylcompound is polymerized with the graft polymer formed in the firststage, the methyl methacrylate comprising from 10% to 80%! of the totalmonomer addition, and the vinyl aromatic monomer comprising from 90% to20% thereof; such polymerization being eifected in an aqueous mediumwhich contains, in relation to 100 parts of total resinous constituents,from 0.5 to 10.0 parts of formaldehyde sulfoxylic salt and effectiveamounts up to 3 parts of peroxides; at least 80% of said butadienepolymer at the start being in the form of particles below 0.2 1 indiameter where the interpolymer is to be blended with vinyl chloridepolymer, and below 0.1; in diameter where the interpolymer is to be usedalone; said butadiene polymeric material constituting out of each 100parts of total resinous constituents, from 20 to 70 parts when theinterpolymer is to be blended with vinyl chloride polymer, and from 20to 60 parts when the interpolymer is to be used alone, the remainder ofeach 100 parts consisting of the sum of the monomeric additions.

This application is a continuation and consolidation of our applicationSer. No. 470,193, filed July 7, 1965, and Serial No. 502,396, filed Oct.22, 1965, both now abandoned. Both of said applications claim priorityfrom Jan. 25, 1965, on which date corresponding applications were filedin Japan.

The present invention relates primarily to a method of manufacturingthermoplastic vinyl resin polymers, and it is specifically concernedwith the eflicient production, on an industrial scale, of aninterpolymer formed by polymerizing a rubbery butadiene polymer withmonomeric methyl methacrylate to form a graft polymer, and thereafterpolymerizing the graft polymer with monoethylenically unsaturatedaromatic hydrocarbon. The thermoplastic butadiene interpolymer soproduced is independently useful as a molding material which yieldsproducts having excellent impact resistance and transparencycharacteristics heretofore deemed mutually exclusive. The interpolymer can alsobe blended with resinous material of the vinyl chloride type to formhighly useful thermoplastic compositions having enhanced impactresistance and transparency.

Vinyl chloride, methyl methacrylate and other vinyl monomers are widelyused in the production of thermoplastic resins. Such products have ahighly desired combination of properties; they are transparent, readilyworkable, resistant to chemicals and heat, and have high electricalinsulating qualities, etc. In addition, they are light in weight andcheap in cost. For these reasons the vinyl plastics are widely used.

However, most of these plastics have a common weakness in that they havelittle impact resistance, which, naturally, restricts the range of theirapplications.

For the purpose of improving their low impact resistance, methods ofvariously binding or blending rubbery material with vinyl resins havehitherto been proposed or attempted (refer to Japanese patentpublications 531293, 567538, 58-2791, 598136, 64-22l92, 60-3534, 61-9593and 626720, etc.).

While many of these attempts have achieved considerable success inimproving impact resistance, which was their objective, neverthelessthey have done so only by simultaneously reducing the transparency ofthe plastic. The end products of these prior techniques were inevitablyopaque and their potential utility greatly restricted, sincetransparency is one of the most important and highly desired propertiesof thermoplastic materials.

The present inventors have long endeavored to create vinyl-basethermoplastic materials possessing both excellent impact resistance, andalso high transparency. The present invention affords an answer to thisproblem.

In essence, the improvement of this invention embraces a novel procedurefor producing an interpolymer of butadiene with methyl methacrylate andmonoethylenically unsaturated aromatic hydrocarbon, which interpolymeris independently useful as such, but can also be blended in conventionalways with vinyl chloride polymers to further enhance desirable plasticproperties.

The improvement of this invention whereby the resulting interpolymer hashigh impact resistance and also is transparent involves forming theinterpolymer from butadiene, methyl methacrylate and a monethylenicallyunsaturated aromatic hydrocarbon, in two stages. In the first stage arubbery butadiene polymer is polymerized to form a graft polymer withmonomeric methly methacrylate. The first stage polymerization is carriedout in an aqueous dispersion and in the presence of formaldehydesulfoxylic salt and peroxide. In the second stage the butadiene-methylmethacrylate graft polymer is polymerized with monomericmonoethylenically unsaturated hydrocarbon to form the interpolymer. Theinvention is further characterized in that more than of the dispersedbutadiene particles employed in the first stage of polymerization areless than 0.1,n in diameter. The invention is also characterized in thatthe polymerization reactions are carried out in the presence of from 0.5to 10 parts (usually from about 2 parts to about 5 parts) offormaldehyde sulfoxylic salt per parts of total resinous constituentsand in the presence of a catalytically effective quantity of peroxidenot in excess of 3 parts (usually from 0.1 to 1.4 parts) per 100 partsof total resinous constituents. A further characteristic of theinvention is that the butadiene in the interpolymer does not exceed 60%of the weight thereof, the methyl methacrylate constituting from 10% to80% by weight of the total monomers that were polymerized with thebutadiene in the first and second stages.

Where the interpolymer is to be blended with a vinyl chloride resin, theratio of the butadiene to the vinyl aromatic in the interpolymer can beincreased. Thus, in such cases and in relation to each 100 parts oftotal polymerizable materials used in forming the interpolymer, one canuse from 20-70 parts by weight of butadiene polymer and from 8030 parts(combined weight) of monomeric methyl methacrylate and monoethylenicallyunsaturated aromatic hydrocarbon. Of the monomers from 10% to 80% shouldbe methyl methacrylate and from 90% to 20% should be themonoethylenically unsaturated hydrocarbon. However, if the interpolymeris to be used as such, it is preferred to limit the butadiene polymercontent of the interpolymer to from 20-60 parts of the total resincontent, increasing the range of monomeric addition correspondingly.

Further, where the interpolymer is to be blended with vinyl chloridepolymer, more than 80% of the particles of the butadiene polymer in theinitial aqueous dispersion must be less than 0.2;; in diameter. Wherethe interpolymer is to be used as such, however, more than 80% of thebutadiene particles should be less than 0.1,u in diameter, in order tosimultaneously maximize the impact resistance and transparency.

As used herein the term rubbery butadiene polymers refers topolybutadiene and/or copolymers comprising from at least 50% butadieneand olefinic monomers having a capacity to polymerize therewith (e.g.acrylonitrile acrylic ester, methacrylic ester, vinyl aromaticchloroprene, etc.). They may be used singly or in mixtures of two ormore kinds. Moreover, they are used in the state of an aqueousdispersion, more than 80% of the particles of which are less than 0.1 uin diameter, where the butadiene interpolymer is to be used as such, orless than 0.2g in diameter where the interpolymer is to be blended witha resin of the vinyl-chloride type.

The vinyl aromatic monomers useful herein include: styrene, a-methylstyrene, a-ethyl styrene or nucleic replaced derivates (e.g., vinyltoluene, isopropenyl toluene, chlorostyrene, etc.). These can be usedsingly or in a mixture of two or more different kinds. They aresometimes referred to herein as monoethylenically unsaturated aromatichydrocarbons.

As the formaldehydesulfoxylic salts to be used, may be mentioned sodiumformaldesulfoxylate (NaSO CH OH 2H O) zinc formaldehydesulfoxylate(Zn[SO CH OH etc., these being used either singly or in mixtures of twoor more kinds.

As the peroxides to be used, may be mentioned organic and inorganicperoxide, e.g. cumenehydroperoxide, diisopropylbenzene hydroperoxide,tertiarybutylhydroperoxide, ditertiarybutylperoxide,methylethylketoneperoride, lauroylperoxide, benzoylperoxide, ammoniumpersulfate, sodium persulfate, potassium persulfate, hydrogen peroxide,etc., these being used singly or in mixtures of two or more kinds.

The vinyl chloride polymers used in this invention for blending with theinterpolymer include: polyvinyl chloride and/ or a copolymer of vinylchloride more than 70% by weight and a monoolefinic monomer, less than30% by weight, capable of copolymerization therewith (e.g. vinylacetate, vinylidiene chloride, ester methacrylate, acrylonitrile, etc.may be mentioned). These may be obtained either by the method ofemulsification, suspension or any other method.

A description will first be provided below of the method ofmanufacturing the interpolymer. In polymerization described herein, anemulsifier is employed.

An aqueous dispersion of the butadiene polymer, described above, isagitated. This system may include, in addition to the emulsifier, apolymerization initiator, polymerization regulator, latex stabilizer,etc.

First, methyl methacrylate is added, which then is polymerized with thebutadiene polymer and after this polymerization is substantiallyfinished, vinyl aromatic is added and polymerized, still in the presenceof the formaldehydesulfoxylic salts and peroxide. Addition andpolymerization of the monomer is commenced while the diameter of morethan 80% of the particles of the dispersion remains below the statedmaxima.

After the polymerization of aromatic vinyl monomer is substantiallycompleted, the aqueous dispersion obtained is salted out and filtered,and its solid content is dried to obtain the interpolymer.

If desired, a thermal stabilizer, light stabilizer, processing agent,filler, coloring agent, or the like may be added. The interpolymer soproduced may then be heated and molded, and thus an article, excellentin impact resistande, may be obtained. Where the interpolymer is to beblended with vinyl chloride resin, it is preferable to delay theaddition of such auxiliary materials until that stage in the processingis reached.

By mixing the interpolymer obtained and vinyl chloride polymer, thedesired compositions, which are excellent both in impact resistance andtransparency, may be obtained. Any conventional method of mixing may beadopted, such as roll-mixing, Banbury mixing or mixing in the state of aliquid dispersion. The relative proportions of these two constituentsmay be varied over a wide range, since the butadiene interpolymers ofthis invention,

like certain other butadiene interpolymers known to the art, areinfinitely compatible with vinyl chloride resins. Even as small anamount as 3% of the butadiene interpolymer will enhance the impactresistance of the composition, and even as small an amount of vinylchloride resin as 40% will improve the workability and transparency ofthe composition.

Salient among the functions and effects of this invention are:

(1) Where the butadiene interpolymer is to be blended with vinylchloride resin, more than by weight of the butadiene polymer particlesin the aqueous dispersion are required to have a diameter smaller than0.2;t.

When butadiene polymer particles not qualifying for the above conditionor having a larger diameter, are used, the compositions obtained, whileindicating a good impact resistance, are deprived of transparency, and,particularly, are inferior in tensile strength. Table 1, below, mayeloquently indicate this fact.

TABLE 1 Relation between diameter of butadiene polymer particles andcharacteristic values. (PVC blend) An aqueous dispersion was used,containing 25% of a copolymer consisting of butadiene 76.5% and styrene23.5%.

To 40 parts of the butadiene/styrene copolymer in said dispersion,sodium formaldehydesulfoxylate, 2 parts, and cumenehydroperoxide, 1part, were added. To this, 30 parts of methyl methacrylate were firstadded and polymerized, and then 30 parts of styrene were added andpolymerized.

13 parts of the resulting interpolymer were roll kneaded with 87 partsof vinyl chloride polymer (degree of polymerization: 1000), for 10minutes att C. The product was pressed for 30 minutes at C. Thetestpiece thus obtained was used.

The impact strength stated is the value at 20 C. by (ASTM D25656; thesame applies hereunder).

The tensile strength stated is the value at 20 C. (ASTMD638-60T; thesame applies hereunder). The transparency stated is the value at 20 C.(118 K6714; the same applies hereunder).

(2) In the presence of formaldehyde sulfoxylic salts and peroxide themonomers mentioned are added and polymerized sequentially. It is notknown why, by so doing, the impact resistance is improved. The mechanismof the catalytic system is not fully clarified yet, but it is assumedthat it is the result of the following important actions.

(a) Mere addition of formaldehyde sulfoxylic salts to an aqueousdispersion of butadiene polymer will not result to any marked extent incoagulation and enlarging of the butadiene polymer particles. The salt,which indicates neutrality in water, slowly disintegrates, and in thepresence of methyl methacrylate (a water-soluble monomer) and peroxide,the dispersed particles are coagulated and swollen smoothly and stably.Thus the re action mass is kept in the state of an aqueous dispersion,and at the same time, graft polymerization on the butadiene polymer iscarried out in parallel.

As a result, a high impact resistance of the composition may beobtained, while its transparency is sufficiently retained. By way ofcontrast, when an aqueous solution of sodium bisulfate and aldehyde isadded to rubber latex, the result will be an immediate drop of pH and aviolent coagulation of the dispersed particles, and, consequently, thestate of an aqueous dispersion is lost, rendering uniform and stablepolymerization impossible.

(b) The formaldehyde sulfoxylic salts, along with the peroxides, effecta crosslinking reaction with the butadiene polymer, so that the impactresistance of the composition is increased.

The factors involved therein are as shown in Table 2.

TABLE 2 This inven- Items tion Control Gel content (percent) ofbutadiene polymer:

Right before the addition of formaldehydesulioxylic salt and peroxide 0.5 Right before the addition of monomer 57. 5 Average diameter ofdispersed particle (p) in aqueous dispersion:

Right before the addition of formaldehydesulfoxylic salt and peroxide 0.07 Right before the addition of monomer 0,07 0. 07 At the time of end ofmethyl methacrylate polymerization 0. 1 0. 08 At the time of completionof entire polymerization 0.15 0. 09 impact strength, izcd with notch(ft. lb./inch) at C Over 12 1.4

REMARKS (a) A rubber latex containing 99% of particles below 0.2 1. indiameter, and containing of a co-polymer consisting of butadiene, 76.5%and styrene, 23.5%, was used.

(b) To parts of the rubber content, 30 parts of methyl methacrylate werefirst added and polymerized, and then 30 parts of styrene were added forpolymerization, and thus the interpolymer was obtained. In the case ofthe polymer mentioned in the item This Invention, hydrate of sodiumformaldehydesulfoxylate, 2 parts, and cumenehydroperoxide, 1 part, wereadded before methyl methacrylate was added. For the Contro onlyconventional amounts (0.4 part) of a standard redox catalyst was added.

(c) 13 parts of the interpolymer were kneaded with 87 parts of a vinylchloride polymer (degree of polymerization: 1000), as mentionedpreviously, and values as shown here were obtained under the sameconditions as in the case of Table 1.

1 ASTM=American Society for Testing Materials. J IS Japanese IndustrialStandard.

TABLE 3 Relation between particle diameter of butadiene polymer andcharacteristic values (interpolymer used per se) This inven- Items tionControl Amount(percent) of particles of butadiene polymer, 99 9 below0.1 in diame r. Impact strength charpy value. 20 "O 25. 5 23.6(Kg./cm./crn. with notch, 30 C. 9. 5 9.0 Tensile strength (kg/cm!) 360320 Transparency:

Coefficient of transmission of visible light 79 45 (percent). Haze value(percent) 5 26 NOTES (a) An aqueous dispersion containing 25 ofco-polymer particles was used. The co-polymer contained 76.5% ofbutadiene and 23.5% of styrene. Against 25 parts of such co-polymer, 3parts of sodium formaldehydesulfoxyl-2 hydrate and 1 part ofcumenehydroperoxide were added, and first, 40 parts ofmethylmethacrylate and 0.2 part of cumenehydroperoxide were added andpolymerized, and then, 35 parts of styrene and 0.2 part ofcumenehydroperoxide were added and polymerized. As a result, the desiredpolymer was obtained.

(b) All of the test pieces were roll-kneaded for 10 minutes at 180 C.,and then press-molded for 30 minutes at 190 C.

(0) Impact strength-HS K6745 Tensile strength-ASTM D63 8-60TTransparency-41$ K6714 The effects of using formaldehyde sulfoxylicsalts and peroxide on the properties of the butadiene interpolymer, perse, are indicated in Table 4.

NOTES An aqueous dispersion containing 99% of the particles of butadienepolymer, used in the experiment of Table 3, less than 0.1 in diameter,was used. The values shown above are those obtained under the sameexperimental conditions as in the case of Table 3.

(3) Butadiene polymer, methyl methacrylate and vinyl aromatic compoundshould be mixed at a fixed ratio.

As mentioned above, 80-30 parts of such monomers containing 10-80% ofmethyl methacrylate and -20% of vinyl aromatic compound are used, asagainst 20-70 parts of butadiene polymer for each parts of total resincontent, when the butadiene interpolymer is to be blended with vinylchloride resin, but from 80-40 parts of monomer in relation to from20-60 parts of butadiene when the interpolymer is to be used as such.When the amount of butadiene polymer is excessively small, a compositionhaving little impact resistance only will result, or the compositionsmay be found to be turbid. If, on the other hand, the amount isexcessively large, the transparency as well as tensile strength of theresulting composition will have deteriorated.

Again, in case the percentage occupied by methyl methamounts increase.Their respective appropriate amounts acrylate in the monomer drops below10%, the resulting are set at 0.5-10 parts for formaldehydesulfoxylicsalt compositions will carry a bluish turbidity, while, in case and lessthan 3 parts for peroxide. In most cases the optiit rises above 80%, itstransparency deteriorates and immum amount lies between about 2 partsand about pact resistance likewise drops. 5 parts.

(4) First, methyl methacrylate (which is slightly waterFormaldehydesulfoxylic salt will not have any noticesoluble) is addedand polymerized, and, after this polymable elfect for coagulation andenlarging of dispersed parerization is substantially completed, vinylaromatic 'comticles, for example, when its amount is 0.1 part againstpound is added and polymerized. 100 parts of resin content, as is usualin conventional By virtue of the two factors, i.e. use of this method ofemulsion polymerization. In case the percentage of methyl polymerizationand the addition of formaldehydesulfoxmethacrylate is below 10%, thefinal polymer will be ylic salt and peroxide, the resulting compositionswill be bluish and non-transparent, while when it is above '80%,provided with a high impact resistance, either in case it thetransparency as well as impact resistance will deis processed at a hightemperature or in case it is procteriorate. essed at low temperatures.Below, this invention will be described in reference to If one proceedseither by polymerizing a mixture of embodiments, two of which illustrateits use where the methyl mcthacrylate and vinyl aromatic co p uinterpolymer is blended with vinyl chloride polymer, and by first addingand polymerizing vinyl aromatic comt o f hi h ho eases wh th i ter l m ipound, and then adding and polymerizing methyl methu d alon acrylate toobtain an interpolymer, the impact resistance 2 E bodi nt 1 shown by theresulting compositions is not found to be adequate. First addition forpolymerization of methyl An aqueous dispersion 160 parts containing ofmethacrylate, a water soluble monomer, is very imporco-polymer parts,99% whereof are below 0.2,u. in diamtant, as detailedly shown in Table5. eter, and comprising 76.5% of butadiene, and 23.5% of TABLE 5Differences due to varying methods of addition of monomer Items Thisinvention Control 1 Control 2 Method of addition of monomer inmanufacture of inter- Addition of methyl meth- Addition of mixture ofAddition of styrene, folpolymer. acrylate, followed by methylmethacrylate and lowed by methyl methstyrene. styrene. acrylate.

Properties of compound:

Impact strength, 20 C. izod with notch (it. lb./ineh) Over 12 4 0 3.5.Transparency as seen by naked eye Transparent Slight bluish turbidityRemarkable blue turbidity. Coeflilcent of transmission of visible 1 1t(percen 80.. 77 72. Haze value (percent) 5 7 11.

REMARKS styrene, were poured, with 65 parts water, into thepolymierizing vessel. Under the flow of a nitrogen current, the Theexperimental conditions were identical as m the dispersion was itated,bein kept at a temperature of case of Table 1. I C. Into the system, 2parts of sodium formaldehyder y W116!e the butadlene P P Y is besulfoxylate dissolved in 15 parts of water, and 1 part of used as such,the effect of coagulation and enlarging of eumenehydroperoxide were dd dParticles y for-maldelflfdesulfoxylic Salt and PeTOXlde IS Thedispersion was thoroughly agitated, and then there stimulated by theaddition first ot a water soluble mon- 45 was added a mixture of methylmethacrylate, 30 parts, omer. consequently, its function is made toprogress and cumenehydroperoxide, 0.2 part. Immediately before smoothly.As a result, the impact resistance is improved, the addition of methylmethacrylate, 98% of the disas indicated in detail in Table 6 below.persed particles of the rubber polymer had a diameter TABLE 6 Items Thisinvention Control 1 Control 2 Method of addition of monomer First methylmethacrylate Mixture of methyl meth- First styrene is added, folisadded, followed by acrylate and styrene is lowed by methyl methstyrcnc.added. acrylate. Impact strength, charpy value, 20 0 25.5 11.6 10.8.(KgJcmJcni. with notch, 30 C 9.5 7.2. 6.9. Transparency:

Coeflicient of transmission of visible light (percent) 79 76 70. Hazevalue (percent) 5.0 6.0 7.5.

NO'DES below 0.2 1.. The conversion ratio of polymerization after Butfor the method of addition of the monomer, the 4 hours was experimentalconditions were identical with those of Then a mixture of styrene, 30parts, and cumenehy- Table 3. 65 droperoxide, 0.2 part, was added. Fivehours later, the

If, out of parts of total amounts of butadiene polypolymerizationconversion amounted to 94%. Here, mer and monomer, the amount ofbutadiene polymer expolymerization was stopped, and the dispersion wascoaguceeds 60 parts (70 parts if the interpolymer is blended lated withhydrochloric acid and sodium chloride, and with poly i yl chloride),tensile strength and transparency was filtered. The solid content wasdried, and, thus, a deteriorate. 70 powder-like interpolymer wasobtained.

The desirable amounts of formaldehydesulfoxylic salt The interpolymer,13 parts, and vinyl chloride resin and peroxide vary according to theconditions of polym- (degree of polymerization: 1000), 87 parts, wererollerization, composition of the monomer, etc. However, so kneaded for10 minutes at 0., along with tin merlong as the stability of thedispersion is not impaired, the captide (stabilizer), 3 parts, and butylstearate, 1 part, impact resistance will be improved according as the 75and press-molded for 30 minutes at C. Thetest pieces thus obtained weretested, and the results shown in Table 7 were obtained.

The impact resistance showed an excellent value at 20 C., whiletransparency on the other hand, was found to be excellent, both inrespect to the percentage of transmission of visible light, which waslarge, and haze value, which was small. Also, the tensile strength andthermal-deformation temperature, likewise, indicated satisfactoryvalues.

Embodiment 2 An aqueous dispersion, 120 parts, containing polymerparticles comprising 76.5% butadiene and 23.5% styrene, 92% of thequantity of which consist of particles below 0.2 in diameter, togetherwith 110 parts water, 2 parts hydrate of sodium formaldehydesulfoxylate,and 1 part isopropylbenzenehydroperoxide, were poured into thepolymerizing vessel similarly as in the case of Embodiment 1, to which,then, a mixture of methyl methacrylate, 40 parts, andisopropylbenzenehydroperoxide, 0.2 part, was added.

Four hours' later, the percentage of polymerization conversion amountedto 94%.

Then, a mixture of styrene, 30 parts, anddiisopropylbenzenehydroperoxide, 0.2 part, was added. Five hours later,the percentage of polymerization conversion rate reached 93%.

The same after-treatment as in Embodiment 1 was carried out, and apowder-like interpolymer was obtained.

60 parts of the interpolymer and 40 parts of a copolymer (degree ofpolymerization: 1300) consisting of vinyl chloride, 95%, and vinylacetate, 5 were rollkneaded for minutes at 180 C., along with tinmercaptide, 3 parts, and butyl stearate, 1 part, and then, was pressedfor 30 minutes at 190 C., and, thus, test pieces were obtained.

The results of test, to which this test piece was subjected, was asshown in Table 8.

TABLE 8 Impact strength, Izod with notch C.) (ft. lb./

inch) Over 12 Tensile strength (kg/cm?) 405 Thermal-deformationtemperature C.) (18.6 kg./

cm?) 75.1 Transparency:

Macroscopical observation Transparent Coetficient of transmission ofvisible light (percent) Haze value (percent) 7 Embodiment 3.Butadieneinterpolymer, per se addition of methyl methacrylate, 98% of thedispersed particles were below 0.1g in diameter. Five hours later,polymerization conversion was 93.5%. To this material, a mixture of 35parts of styrene and 0.2 part of cumenehydroperoxide was added forpolymerization.

Five hours later, polymerization conversion amounted to 93% At thispoint, polymerization was suspended. An aqueous solution of hydrochloricacid and table salt was added for coagulation, filtering and drying,and, thus, a powder-like polymer, 94 parts, was obtained.

The product was roll-kneaded for 20 minutes at C. and pressed for 30minutes at C. From the test piece thus adjusted, the test results ofTable 9 were obtained.

NOTE

The experimental method was the same with the case of Table 3.

Embodiment 4 An aqueous dispersion, 220 parts, containing polybutadieneparticles, 40 parts, 92% thereof being below 0.1 in diameter, sodiumformaldehydesulfoxyl-Z hydrate, 4 parts, dissolved in water, 20 parts,and cumenehydroperoxide, 1 part, were fed into a polymerizing vessel inthe same way as in Embodiment 1. A mixture of methyl methacrylate, 30parts, and cumenehydroperoxide, 0.2 part, was added for polymerization.

Four hours later, polymerization conversion was 95%. Then styrene, 30parts, and cumenehwdroperoxide, 0.2 part, were mixed and added forpolymerization. Five hours later, the polymerization conversion amountedto 94%.

Through a similar treatment as in Embodiment 3, a powder polymer, 96parts, was obtained.

This polymer was tested under the same conditions as in Embodiment 3 andthe results of Table 10 were obtained.

TABLE 10 1. In a process of making a thermoplastic interpolymer frombutadiene, methyl methacrylate and monoethylenically unsaturatedaromatic hydrocarbon, the improvement whereby the resulting interpolymerhas high impact resistance and is transparent, which comprises effectingthe formation of the interpolymer in an aqueous dispersion and in thepresence of formaldehyde sulfoxylic salt and peroxide in two stages, inthe first stage polymerizing a rubbery butadiene polymer with monomericmethyl methacrylate, and in the second stage polymerizing thebutadiene-methyl methacrylate graft polymer so formed with monomericmonoethylenically unsaturated aromatic hydrocarbon to form theinterpolymer; said improvement being further characterized in that morethan 80% of the dispersed butadiene particles employed in the firststage of polymerization are less than 0.1,u in diameter, and in that thepolym- 1 1 erization reactions are carried out in the presence of from0.5 to 10 parts of formaldehyde sulfoxylic salt per 100 parts of totalresinous constituents and in the presence of a catalytically eifectivequantity of peroxide not in excess of 3 parts per 100 parts of totalresinous constituents, and wherein from 20% to 60% by weight of thebutadiene polymer is polymerized in stages one and two with from 80% to40% of the monomeric components to form 100 parts of the interpolymer,the methyl methacrylate representing from 10% to 80% of the total weightof the monomeric materials added in the first and second stages.

2. The improved process of claim 1, wherein the formaldehyde sulfoxylicsalt is present in proportions of from about 2 parts to about 5 parts inrelation to each 100 parts of total resinous constituents.

3. The improved process according to claim 1 wherein the butadienepolymer is polybutadiene.

4. The improved process according to claim 1 wherein the butadienepolymer is a butadiene copolymer containing at least 50% of butadiene.

5. The improved process according to claim 4 wherein the butadienecopolymer is a butadiene-styrene copolymer.

6. The improved process according to claim 1 wherein themonoethylenically unsaturated aromatic hydrocarbon in the second stageof polymerization is styrene.

7. The process of making a thermoplastic composition whereby theresulting thermoplastic composition is highly transparent and also hashigh impact resistance by blending a vinyl chloride polymer containingat least 70% polyvinyl chloride with an interpolymer made in accordancewith claim 1.

8. The process of making a thermoplastic composition whereby theresulting thermoplastic composition is highly transparent and also hashigh impact resistance by blending a vinyl chloride polymer containingat least 70% polyvinyl chloride with an interpolymer made in accordancewith claim 4.

9. The interpolymer produced by the method of claim 1 10. Thethermoplastic composition produced by the method of claim 7.

11. In a process of making a thermoplastic composition by blending avinyl chloride polymer with an interpolymer containing butadiene, methylmethacrylate and monoethylenically unsaturated aromatic hydrocarbon, theimprovement whereby the resulting thermoplastic composition has highimpact resistance and is transparent and which comprises effecting theformation of the butadiene interpolymer in two stages in an aqueousdispersion and in the presence of formaldehyde sulfoxylic salt andperoxide, in the first stage polymerizing a rubbery butadiene polymerwith monomeric methyl methacrylate, and in the second stage polymerizingthe butadiene-methyl methacrylate graft polymer from the first stagewith monomeric monoethylenically unsaturated aromatic hydrocarbon, theresulting interpolymer being thereafter blended with the vinyl chloridepolymer, said improvement being further characterized in that more than80% of the dispersed butadiene particles employed in the first stagepolymerization are less than 0.2 in diameter; and in that thepolymerization reactions are carried out in the presence of from 0.5 to10 parts formaldehyde sulfoxylic salt per 100 parts of total resinousconstituents and in the presence of a catalytically eifective quantityof peroxide not in excess of 3 parts per 100 parts of total resinousconstituents; and in that from 20 to parts by weight of the butadienepolymer are polymerized in stages one and two with from to 30 parts ofthe monomeric components to form parts of the interpolymer, the methylmethacrylate representing from 10 to 80% of the total weight of themonomeric materials added in the first and second stages.

12. The improved process of claim 11, wherein the formaldehydesulfoxylic salt is present in proportions of from about 2 parts to about5 parts in relation to each 100 parts of total resinous constituents.

13. The improved process according to claim 11, wherein the rubberybutadiene polymer is a polymer of butadiene and styrene.

14. The improved process according to claim 13, wherein themonoethylenically unsaturated hydrocarbon is styrene.

15. The thermoplastic composition produced according to the process ofclaim 11.

References Cited UNITED STATES PATENTS 3,287,443 11/1966 Saito et a1.260-876 3,288,886 11/1966 Himei et a1. 260-876 3,296,339 1/ 1967 Feuer260-879 FOREIGN PATENTS 850,487 10/ 1960 Great Britain 260876 MURRAYTILLMAN, Primary Examiner H. ROBERTS, Assistant Examiner US. Cl. X.R.

260-29.7 UA, 880 R

